Various sorting devices for gelatin capsules with an assembly defect are already known and used in production.
A first example of such a device is made of several sieves arranged for forming a cylinder with a horizontal axis. Each sieve has several openings calibrated at a diameter slightly larger, by some hundredths of a millimeter, than that of the gelatin capsules.
The gelatin capsules enter this cylinder through one of its sides. The cylinder rotates to stir the gelatin capsules continuously. The properly closed gelatin capsules pass through the openings of the sieves. On the other hand, those showing an assembly defect remain trapped inside of the sieve, since their deformation does not allow them to pass through the calibrated openings. This system has the following defects:                The ejection of the defects requires a manual intervention of the operator and a complete stoppage of the production machine.        The continuous stirring of the rejects can lead to the passage of a defect through the selection opening.        During a longer operation time, product residues tend to reduce the passage diameter of the calibrated openings, requiring a manual intervention for the cleaning.        
Another machine uses a blowing device to eject the empty (non dosed) or single parts (separated caps and bodies). The disadvantage of this system is that it does not process the gelatin capsules individually. The gelatin capsules are processed in clusters and, quite often, the defective parts cannot be expelled because they are drawn along by the other gelatin capsules.
Publication U.S. Pat. No. 3,997,058 describes another example of an automatic gelatin capsules sorting device. It includes a horizontal disk mounted in rotation above a fixed plate and having on its periphery calibrated openings arranged so as to receive only one gelatin capsule at a time. The fixed plate is spaced away from the disk by a distance slightly larger than the length of a gelatin capsule cap. This way, the single gelatin capsules, which are shorter than the conforming gelatin capsules, fall directly through the openings and are collected on the fixed plate and evacuated by vacuum means, while the properly assembled gelatin capsules are retained above the fixed plate in the various openings, before being evacuated by gravity during the rotation of the disk. The gelatin capsules having a diameter larger than that of a conforming gelatin capsule are retained on the upper surface of the disk and evacuated by vacuum means. Although this system facilitates processing of the gelatin capsules individually, it does not give satisfaction at the present time, since it is particularly complex and expensive, as it requires three sorting and evacuation levels.